1. Field of the Invention
The present invention pertains to a pressure plate assembly comprising a housing arrangement; a pressure plate mounted in the housing arrangement with freedom of movement in a direction parallel to the axis of rotation; and a force-exerting arrangement, preferably a force storage device, supported against the housing arrangement and the pressure plate. A wear take-up device in the path of force transmission between the pressure plate and the force-exerting arrangement includes at least one take-up element which can be shifted to compensate for wear; a blocking element on the pressure plate with a detecting section which can come to rest against a stop upon the occurrence of wear and which is able to move with respect to the pressure plate; and a wedge-like arresting element, which arrests the blocking element and thus prevents it from returning to its previous position after it has moved with respect to the pressure plate. The arresting element is pretensioned by a pretensioning arrangement in the direction toward a state in which it prevents the blocking element from returning to its previous position.
2. Description of the Related Art
In pressure plate assemblies of this type, the arresting action of the arresting element is usually achieved by a pretensioning effect, usually produced by a pretensioning spring, which pretensions the element into an intermediate space formed between the blocking element and the pressure plate. This intermediate space increases in size as the amount of wear increases, and the wedge-like arresting element can thus shift correspondingly and move continuously farther into this space. The pretensioning effect which tries to push the arresting element into the intermediate space indicated, however, also exerts a force on the blocking element, namely, a force which tries to shift it in the same direction as that in which it would move with respect to the pressure plate after the occurrence of wear. If such a shift of position were to occur, this could cause the take-up element, at least one of which is present, to execute a wear-compensating or wear take-up movement even though no wear has occurred. To prevent this, the blocking element, which is usually designed as a leaf spring, can be provided with an intrinsic pretensioning force strong enough to prevent the arresting element from causing this type of undesirable movement(of the blocking element. Providing the blocking element with enough stiffness to accomplish the end result, however, leads to the problem that, after it has made contact with the stop, the blocking element must be deformed in opposition to its intrinsic stiffness. This type of actuation of the blocking element usually occurs during the clutch-engaging operation, but because of the stiffness of the element, a force acting in opposition to the displacement of the pressure plate, which carries the blocking element, is generated.